I recently unlocked a beard style (for APs), but when I try to put it on my avatar it won't show up. Then I noticed that I have problem with the other - locked - beard items too (although I click on 'Preview' they cannot be seen on my avatar either). Other wardrobe things (eyes, clothing, items, etc.) work fine. I tried to log out, clear my cache/cookies, then log in again, but the problem still occurs.

Edit: I think the problem is caused by Winter Fawn's Horns, without that head item beards work fine too.

Yea. By default, full helms remove ears/hair/beards. For some full helms, we make exceptions for ears/beards to be visible.

However, since the Winter Fawn's Horns have built in ears, this is not the case - so beards are disabled as well.